Acyclovir Dosing for Shingles (Herpes Zoster)
For acute treatment of shingles, the recommended dose of Zovirax (acyclovir) is 800 mg orally five times daily for 7 to 10 days, initiated within 72 hours of rash onset for maximum benefit. 1
Standard Oral Dosing Regimen
- The FDA-approved dosing for herpes zoster is acyclovir 800 mg orally every 4 hours, five times daily for 7 to 10 days 1
- This high-dose regimen (800 mg five times daily) is significantly superior to lower doses (400 mg five times daily), demonstrating accelerated viral clearance, faster time to 50% scabbing and healing, reduced new lesion formation, and decreased severity of acute pain 2, 3
- Treatment must be started within 72 hours of rash appearance for optimal efficacy 4
Intravenous Therapy for Severe Disease
- For severe disease, complications, disseminated zoster, or hospitalized patients, the CDC recommends acyclovir 5-10 mg/kg IV every 8 hours for 5-7 days or until clinical improvement 5
- IV therapy is particularly important for immunocompromised patients to halt viral dissemination and prevent visceral complications 3
- At these higher IV doses, adequate hydration and urine flow must be maintained, mental status monitored, and dosing adjusted downward for impaired renal function 3
Renal Dose Adjustments
- For creatinine clearance 10-25 mL/min: reduce to 800 mg every 8 hours 1
- For creatinine clearance 0-10 mL/min: reduce to 800 mg every 12 hours 1
- For hemodialysis patients, administer an additional dose after each dialysis session due to 60% reduction in plasma concentrations during a 6-hour dialysis period 1
Special Populations: Immunocompromised Patients
- Immunocompromised patients (including HIV-infected individuals) require more aggressive therapy with higher doses or IV administration 5, 6
- For AIDS patients with herpes zoster, one approach is 800 mg oral acyclovir five or six times daily for 5-10 days depending on response, with potential benefit from concomitant topical acyclovir 6
- These patients may need suppressive therapy with acyclovir 400 mg orally 3-5 times daily to prevent recurrences 5
Critical Timing Considerations
- Therapy should be initiated within 72 hours of rash onset - treatment started after this window has significantly reduced effectiveness 4
- Early initiation during the prodrome or at first sign of lesions provides maximum benefit for reducing acute pain duration and severity 2
Important Caveats to Avoid Common Pitfalls
- Never use topical acyclovir for herpes zoster - it is substantially less effective than oral therapy and provides no meaningful clinical benefit 5
- Acyclovir does not eradicate latent varicella-zoster virus and does not prevent future recurrences after discontinuation 5
- While the 800 mg five times daily regimen reduces acute pain and may decrease early postherpetic neuralgia (particularly in the first 3 months), it has not been definitively proven to prevent long-term postherpetic neuralgia 2, 7
Alternative Antiviral Options
- Valacyclovir 1000 mg three times daily for 7 days offers comparable efficacy with simpler dosing (accelerates pain resolution with median duration 38 days versus 51 days for acyclovir) and maintains the favorable safety profile 7
- Famciclovir 500 mg twice daily for 7 days demonstrates comparable efficacy to acyclovir 800 mg five times daily with more convenient dosing 4